Communications systems typically include several components which are interconnected via signal-carrying paths or communications links. Such communications links can be realized using a variety of different technologies including twisted pair, coaxial cable, optical fibers and radio. Many communications systems contains computerized diagnostics which can quickly determine the existence of a fault. However, once it has been determined that the fault is due to a problem in a communications link, correction of the fault typically requires either the tracing of the troublesome link to determine the precise location of the fault or the reassignment and replacement of the same with one or more spare communications links.
While the use of a spare communications link advantageously avoids the need to locate the fault, such spares are not always available. Indeed, the availability of such spares in communications systems which were wired at the time of installation and whose burgeoning growth and accompanying demand for interconnections have severely drained the initial allocation of spare communications links. Moreover, the installation of additional communications links after installation to restore a sufficient allocation of spares is oftentimes difficult, if not impossible, in many system environments.
The task of tracing and correcting interconnection problems in large communications systems, e.g., switching systems and private branch exchanges (PBXs), which include a large number of communications links, is a time-consuming and costly process with a substantial portion of the time and expense being associated with link tracing. One process of link tracing involves the use of two craftspersons. One craftsperson starts at a point in the link where a problem has been detected and proceeds to trace this link and successively apply signals at selected points in order to determine the location of the fault. At each point, the craftsperson tracing the link generally dials another craftsperson located at a system administration console. This step verifies that the troublesome link, and not some other, is being traced and that signal continuity is present. While this technique provides satisfactory results, the time and expense associated with the coordination of the work of two craftsperson oftentimes exceeds system objectives and does not meet customer demands for the rapid restoral of communications services.
Another tracing procedure involves the attachment of a radio transmitter having a predetermined transmitting frequency to the defective communications link so that the latter serves as an antenna. Tracing this link is then accomplished by following the route of the link with a radio receiver. The radio receiver is tuned to the transmitter's transmitting frequency so that the receiver will respond with an audible signal or will display a noticeable deflection of the receiver's signal strength meter when the receiver is close to the communications link. When the receiver ceases to respond, the location of the fault is determined, assuming that the route of the defective link has been properly followed. There are several shortcomings with this procedure. The first is that it is easy to inadvertently deviate from the route of the defective link and thereby cause a cessation of the receiver's response even though the location of the fault has not been located. Second, this technique, in areas where there are many densely-packed interconnections, e.g., an interconnection closet or cross-connect field, cannot locate the traced communications link or the fault therein. Finally, the radiation of the radio signal from the wire pair antenna interferes with the operation of voice and data communications devices utilizing links adjacent to the defective one. This interference, which results in a mildly-annoying tone in a voice circuit, can completely interfere with certain data communications protocols and render data communications unintelligible.
Therefore, it would be extremely desirable if a scheme for tracing communications links which did not have the prior art limitations could be devised.